Soccer superstar Kylian Mbapp missed Real Madrids Club World Cup opening game Wednesday, and the team revealed the reason.Real Madrid said Thursday that Mbapp was hospitalized due to acute gastroenteritis. The team added Mbappe is going through "a series of tests" and will "follow the appropriate course of treatment" after getting results.Acute gastroenteritis is like the stomach flu, but there are differences.CLICK HERE FOR MORE SPORTS COVERAGE ON FOXNEWS.COMMbapp, 26, began experiencing symptoms Monday and missed Real Madrids practice Tuesday.CHAOS ENSUES AT FIFA CLUB WORLD CUP GAME, INCLUDING PETA PROTESTERS INVADING FIELD, SMOKE FLARESThe team didnt say he wouldnt be available for the game Wednesday, and head coach Xabi Alonso noted the team would "wait until the last minute" to decide on his game status, according to The Athletic.After Real Madrid finished with a draw against Al Hilal, Alonso said Mbapp's illness was worse than originally thought.Mbapp's timeline to return is now uncertain.Real Madrid has a game scheduled for Sunday against Pachuca in the Club World Cup.Mbapp is in his first season with Real Madrid, scoring 43 goals in 56 appearances for the Spanish club.Mbapp and the French national team will look for redemption in next years FIFA World Cup after losing to Argentina in the final in 2022.Follow Fox News Digitalssports coverage on X, and subscribe tothe Fox News Sports Huddle newsletter.